Solving this debt is not that tricky, it has known legal solutions - e.g. when you have a court order to collect debts from you, where your wages are garnished, it has a floor limit of monthly income that's untouchable and that monthly amount will be available on your bank account no matter what, and there are no legal ways to recover that from you. Threatening to break your legs may work, but that can be handled by the police.

Set this floor equal to BI, and that's it. On the other hand, it will mean that payday lenders will likely not lend to you at all if you have no other income, since you can easily never ever pay them back with impunity; but that might be considered a good thing - people won't get stuck with predatory loans en masse because they won't be given them.